1. Field of the Invention
The invention relates to hole saws and arbor constructions for performing high-speed power-driven circular hole sawing operations. More particularly, the invention relates to a construction in which the hole saw and arbor are formed as an integral unit for each particular hole size in order to reduce hole saw tooling costs and the time and effort of assembling a hole saw on a separate arbor.
2. Description of the Prior Art
Most hole saw tooling consists of one or more arbors on which is mounted the desired size of an annular cylindrical hole saw blade. The blade has an end cap with a threaded opening which is engaged with a threaded shank of the arbor or is clamped thereon by a retaining nut mounted on the threaded arbor shank. The arbor also may be provided with a plurality of drive pins which extend through openings formed in the end cap of the saw blade.
There are various hole saw blade types manufactured by different saw blade producers. Usually, each type of hole saw blade requires a particular arbor construction for mounting the saw blade on a drive mechanism. Some interchangeability between various saw blade types and their mounting arbors exists in order to reduce the amount of hole saw components.
One type universal hole saw arbor is described in my U.S. Pat. No. 3,647,310. Such an arbor reduces considerably the amount of hole saw and arbor components required for a hole saw tooling, and permits interchangeability between the components of various manufacturers. Considerable time and effort, however, is still required for assembling hole saws on their arbors each time a change in hole size is required. This joined hole saw and arbor assembly in turn must be mounted on the driving chuck of the power drive mechanism.
Studies have shown that when separate arbors are used, approximately 60% of the cost of a single hole saw blade and arbor is due to the arbor. This cost, however, is reduced where additional hole saw blades are purchased that can be mounted on the same arbor. These studies have shown that approximately 35% of the average hole sawing tool costs incurred by purchases of saw blades and arbors are for the arbors.
The use of separate saw blades removably mounted on an arbor heretofore was desirable to eliminate replacing the arbor and drive stem each time replacement of the saw blade was required because of wear, due to the relatively expensive cost of the arbor in contrast to the cost of the saw blade. This high arbor cost is due to the complicated and sometimes elaborate arbor constructions required for mounting of the various saw blades thereon.
Various prior art hole saws and arbors have been devised which eliminate the use of a threaded arbor shank or retaining clamping nut for mounting of a hole saw blade on the arbor prior to mounting the same on the chuck of a power drive mechanism.
The hole saw of U.S. Pat. No. 2,444,099 eliminates any such threaded clamping nut which engages the threaded shank of an arbor stem for mounting the hole saw thereon by providing a tapered connection between the arbor stem and saw blade. This patent states that the cutting element may be formed integrally with the shank, but indicates that a two-piece construction is preferable and does not disclose any such integral construction. It is believed that it would be difficult for such a tapered connection to be able to transmit the high torques required for many sawing operations without slipping. Furthermore, saw blades similar to that of this construction would be expensive to mass produce.
U.S. Pat. No. 2,800,812 discloses a shell cutter assembly in which a cutting blade is welded to a hollow socket, which combination then is subsequently assembled to the bore of a machine by a plurality of mounting openings. A pilot drill is mounted by a threaded connection within a corresponding threaded bore formed on the cutting blade. Again, such a cutting blade and associated pilot drills would be relatively expensive to mass produce due to the threaded bore and shank for mounting the drill on the cutting blade.
U.S. Pat. No. 3,550,229 shows various hole saw blades and arbor constructions, one of which has the cutting blade formed integrally with a solid tubular stem. Such a construction prevents the use of a pilot drill with the blade which is desirable for most hole saw cutting operations because of such a solid stem construction. Another construction of this patent shows a cutting saw blade having an end cap and setscrew mounted therein for adjustably mounting a pilot drill on the saw blade. Again, such constructions are relatively expensive to mass produce due to the machining and manufacturing procedures required to produce such arbor and blade constructions.
Still another type of known hole saw and arbor construction is shown in U.S. Pat. No. 3,648,508. This construction provides a separate end cap to which a cylindrical hole saw blade is mounted by a tapered drive fit, enabling low cost cylindrical hole saw blades to be used. However, such a construction is not formed as an integral unit, but comprises a plurality of separate components detachably joined together.
Thus, there is a need for an integral hole saw and arbor construction which can be produced economically and yet still provide the necessary hole sawing qualities by integrally joining these inexpensively produced components which enable the arbor to be discarded with the saw blade when the blade becomes worn, and which will eliminate the time consuming assembling of the individual hole saw blades on the arbor prior to mounting the assembly on a power drive mechanism.